The mol­ecule of the title compound, C14H13N3O, adopts an E conformation with respect to the azomethine C=N bond, and is roughly planar, with an r.m.s. deviation of the non-H atoms from the least-squares plane of 0.100 (2) Å and a dihedral angle between the terminal benzene rings of 5.74 (12)°. An intramolecular N—H⋯N hydrogen bond closes an S(6) ring. In the crystal, mol­ecules are linked by the pairs of N—H⋯O hydrogen bonds into centrosymmetric dimers. Dimers related by translation along [010] form slanted stacks, the shortest C⋯C inter­molecular distance within the stack being 3.283 (3) Å. Weak C—H⋯π inter­actions link the stacks into a three-dimensional structure.

Hydrazinecarboxamides with versatile structural features are good ligands for both the neutral and anionic complexes (Rivadeneira et al., 2009). The aryl hydrazinecarboxamides were found to be devoid of sedative hypnotic activity and exhibited anticonvulsant activity with less neurotoxicity (Shalini et al., 2009).

The title compound (Scheme 1, Fig. 1) crystallizes in the monoclinic space groupP2/c. The molecule adopts an E configuration with respect to C7═N1 bond and the N3–C8–N2–N1 torsion angle of 4.3 (3)° reveals that N1 and N3 atoms are cis to each other with respect to C8—N2 bond. The central fragment N3–C8(O1)–N2–N1 is almost planar and forms diherdal angles with two benzene rings of 13.24 (11)° (C1—C6) and of 7.60 (12)° (C9—C14).

The C7—N1 (1.273 (2) Å) and C8—O1 (1.225 (2) Å) bond distances are very close to the reported bond lengths of azomethine and keto groups, respectively, in similar structures (Annie et al., 2012), confirming the azomethine bond formation and existence of semicarbazone in amido form. A five-membered ring is formed by N1/N2/C8/N3 and H3' through an intramolecular H-bonding interaction with a D···A distance of 2.634 Å. In the crystal, a centrosymmetric dimer (Aravindakshan et al., 2013) is formed by means of a classical intermolecular N—H···O hydrogen bond (Fig. 2) with a D···A distance of 2.860 (2) Å. A C—H···π interaction (Fig. 3) is present in the crystal between the hydrogen attached to the carbon C3 and the C9—C14 benzene ring with H···π distance of 2.99 Å, interconnects the adjacent centrosymmetric dimers to build a three-dimensional supramolecular architecture in the system. Fig. 4 shows the packing diagram of the title compound along b axis.

The title compound was prepared by adapting a reported procedure (Siji et al., 2010). Hot methanolic solutions (25 ml) of equimolar amounts of benzaldehyde (0.106 g, 1 mmol) and N-phenylhydrazinecarboxamide (0.151 g, 1 mmol) were mixed and refluxed for 3 h after adding a few drops of dilute acetic acid. The resulting solution was cooled to room temperature. The colourless block shaped crystals were collected, washed with few drops of methanol and dried over P4O10in vacuo. Single crystals suitable for X-ray analysis were obtained by slow evaporation of solution in air for few days.

All H atoms on C were placed in calculated positions, guided by difference maps, with C—H bond distances of 0.93 Å. H atoms were assigned Uiso(H) values of 1.2Ueq(carrier). H atoms of N3—H3' and N2—H2' bonds were located from difference maps and the bond distances are restrained to 0.88±0.01 Å.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Acknowledgements

We thank the Indian Institute for Science Education and Research (IISER), Thiruvananthapuram, for the diffraction measurements. LSR thanks the CSIR, New Delhi, for the award of a Junior Research Fellowship.

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